The invention relates to the electric engineering area, i.e. in particular to a solid state electrochemical current sources, in which the anode, the electrolyte, and the cathode are present in the solid phase condition.
The source of the invention may find the following applications:
In primary built-in batteries used in systems of a continues operation, and with a long service life at a normal temperature;
In primary autonomous batteries to be used at high temperatures;
In back-up batteries to be used by rescue teams, if heated. Such batteries may have a different power output, and operation duration, while these may be used in order to start diesed engines.
Definitions
simple fluorides single metal fluoride compounds selected from the group consisting of CoF3, PbF3, MnF3, TaF5, NdF35l , HgF2, CuF2, AgF, AgF2, BiF3.
composite fluorides fluoride compounds that contain at least two metals with different valences
compound fluorides fluoride compounds that contain at least two metals with different valences
In the world, the following solid state electrochemical batteries are known which are disclosed in U.S. Pat. No. 4,216,279 published on Aug. 5, 1980 and in U.S. Pat. No. 4,215,827 published on Aug. 19, 1980, HOIM 6/18), where the anode is made of lead or its alloys; the electrolytes are made of composite fluorides based on PbF2 with such additives as SrF2, BaF2, or CaF2, and the KF admixture; as well as the electrolyte made of PbF2xe2x80x94SnF2, or PbF2xe2x80x94SnF2xe2x80x94KF; while the cathode is made of simple fluorides chosen from the following group: CoF3, PbF3, MnF3, TaF5, NdF5, HgF2, CuF2, AgF, AgF2, BiF3 in the mixture with the manganese oxide (U.S. Pat. No. 4,216,279, HOIM 6/18) in the mole ratio of MnO2/metal fluoride as 1:2.5, and about 3:1. The above mentioned manganese oxide has the content of water from 1 to 25% of mass. U.S. Pat. No. 4,218,527, HOIM 6/18 discloses as well the cathode, which is the mixture of one of the above mentioned simple fluoride, and the lead oxide in the m/o ratio of PbO2, (metal fluoride as 3:1, and 1:3). The content of water in the aforementioned lead oxide is from 0.4% till 10% of mass.
These well-known batteries including the cathode, which is made of the mixture of xcex1-non-composite metal fluoride with the manganese or lead oxide with a certain water content, have a limited operational temperature range as regards the battery discharge behavior, due to the presence of water in the cathode mixture, while this may be the reason of an unstable battery behavior.
The drawback of the aforementioned well-known batteries is their low energy capacity, which is associated with a low energy capacity of the interaction between the fluoride and lead in the anode. Theoretically, the energy capacity of the interaction between the fluoride and lead in the anode is 259 Axc2x7h/kg (of the anode weight), or 27.65 Axc2x7h/cm3 (of the anode weight). Besides, these batteries have a low open circuit voltage, i.e. the OCV is 1.36-1.94 V according to the testing results disclosed in U.S. Pat. No. 4,216,279, and OCV is 1.85-1.95 according to the testing results disclosed in U.S. Pat. No. 4,218,527.
The battery, which is the most close to the current source of the invention, is that disclosed in the European Patent EP 0055135 B1, HOIM 6/18. This battery comprises the anode, which is made of a metal chosen from the group of Li, Sr, Ba, Ca, Mg, Ce, La, alloys of Ce, La, Mg; the solid electrolyte, which is basically the composition of 70 m/o of the cerium or lanthanum fluoride, at least one fluoride, chloride, or carbonate of an alkaline earth metal and one fluoride, chloride or carbonate of an alkaline metal; and the cathode, which is made of the ion conducting composite fluorides including two metals with different valency, in particular, the ion conducting composite salts such as KBiF4, TIBiF4, RbBiF4.
The disadvantage of such technical decision is a low OCV. E.g. the battery including the anode made of Ce, or La; the CeF3xe2x80x94SrF2xe2x80x94LiF electrolyte, and the PbSnF4xe2x80x94based cathode has the OCV of 2.28 V. The use of the anode made of a pure lanthanum, and of the cathode made of pure PbF2 did not change the OCV magnitude.
The low OCV of the aforementioned well-known batteries causes the decrease of their power output behavior, which in its turn imposes a certain limitations on the number of practical applications of the batteries.
Besides, one of the essential drawbacks of the above mentioned battery type is its limited operational temperature range in a solid phase condition. The metals which are being reduced during the discharge in the cathode composition have as a rule, a low melting point (e.g. Rb, Bi, Tl). That is way the temperature range of the solid phase reactions is limited by this point. So, such batteries have a low fire resistance, as well as a low stability with regard to other accident effects, due to the limited stability of the solid phase of the battery components.
The task, which is addressed in the present invention, is the enhancement of technical and operational parameters of the solid state current source, i.e. the upgrading of its OCV; of its power output behavior during the discharge; and widening of its operational temperature range in the solid phase condition.
The technical results, which may be reached provided the use of the present invention, are the following:
The OCV is enhanced from 2.74V (of the prototype) till 3.9V.
The power output number is increased by factor of two in relation to the prototype;
The source""s operational temperature range in the solid phase condition is increased from 271xc2x0 C. (of the prototype) till 500xc2x0 C.
In order to accomplish the aforementioned task of the invention, into a well-known battery including the anode, the ion conducting electrolyte, and the cathode, which is an ion conducting composite fluoride formed by at least two metals with different valences, it was introduced a metal oxide into the cathode composition, provided the following mole percentage of the components are observed:
a composite fluoride: 11.5-96.9 m/o;
a metal oxide: 3.1-88.5 m/o.
The invention relates to the current source, in the cathode of which it is used copper oxide (CuO), lead oxide (PbO2), manganese oxide (MnO2), vanadium oxide (V2O5), or silver oxide (Ag2O).The composite fluoride of the cathode is the solid solution of vithmuth fluoride and potassium fluoride, or the solid solution of lead fluoride with potassium fluoride. The anode of the source is either made of a metal from the group of rare earth metals, or of an alloy of such a metal. The electrolyte is a solid fluoride ion conductor including at least one fluoride of a rare earth metal, and at least one fluoride of an alkaline earth metal.
The invention relates to the solid state current source, in which the current producing reaction is possible due to the fluoride ions transport from the cathode, and due the interaction of these ions with the anode material. The viability of the ion transport is determined by the electric driving force (EDF) of the source, which practically corresponds to the measured numbers of the source""s open circuit voltage (OCV). The character of the current producing reaction depends on the fluoride ion conductivity of the electrolyte material, on that of the composite fluoride comprised in the cathode, and on that of the fluoride, which is formed as a result of the interaction of the anode material with fluoride ions.
It was experimentally proved that:
1. The OCV of the solid state current source considerably increases, if the cathode contains the mixture of the ion conducting composite fluoride and the oxide;
2. The use of the mixture of the ion conducting composite fluoride and the metal oxide as the cathode in the aforementioned batteries leads to their discharge voltage increase. This finally defines the enhancement of the specific power of the discharge of the current sources.
In distinction from other well known batteries of similar type (i.e. disclosed in the U.S. Pat. Nos. 4,216,279 and 4,218,527), in which the mixture of a simple fluoride with PbO2, or MnO2, is used as the cathode, along with a certain water content in the aforementioned oxide, the latter condition is not obligatory as regards the current source of the present invention. In the cathode of the source of the present invention, which contains the ion conducting composite fluoride and metal oxides, the fluoride ion conductivity preserves in the solid phase condition of the source, and this source in a stable way discharges without a water content in the oxide of the cathode. The aforementioned oxide reacts with the metal, or metals of the composite fluorides of the cathode which leads to the increase of the EDF, and power output behavior upgrading.